use futures_util::SinkExt;
use ldap3_proto::LdapCodec;
use ldap3_proto::control::*;
use ldap3_proto::proto::*;
use tokio::io::AsyncWrite;
use tokio_util::codec::FramedWrite;

use std::sync::Arc;

use crate::{BasicLdapClient, ClientState, Config, Dn, LdapError};

pub fn bind_operror(msgid: i32, msg: &str) -> LdapMsg {
    LdapMsg {
        msgid,
        op: LdapOp::BindResponse(LdapBindResponse {
            res: LdapResult {
                code: LdapResultCode::OperationsError,
                matcheddn: "".to_string(),
                message: msg.to_string(),
                referral: vec![],
            },
            saslcreds: None,
        }),
        ctrl: vec![],
    }
}

pub async fn bind<W: AsyncWrite + Unpin>(
    w: &mut FramedWrite<W, LdapCodec>,
    mut lbr: LdapBindRequest,
    config: Arc<Config>,
    msgid: i32,
    ctrl: Vec<LdapControl>,
) -> Result<Option<ClientState>, LdapError> {
    trace!("{:?}", lbr);

    if lbr.dn == "" {
        // Here we pretend to have successfully bound so that
        // a client performing an anonymous bind can proceed with
        // more requests (such as a search request).
        // This supports ldap search which always performs a bind.
        let resp_msg = LdapMsg {
            msgid,
            op: LdapOp::BindResponse(LdapBindResponse {
                res: LdapResult {
                    code: LdapResultCode::Success,
                    matcheddn: "".to_string(),
                    message: "".to_string(),
                    referral: vec![],
                },
                saslcreds: None,
            }),
            ctrl: vec![],
        };
        w.send(resp_msg).await.map_err(|err| {
            error!("Unable to send response: {err}");
            LdapError::Transport
        })?;
        // We still treat the client as unbounded because it doesn't
        // have a session to a backend.
        return Ok(Some(ClientState::Unbound));
    }

    let request_dn = lbr.dn.clone();

    debug!("Received bind request on DN: {}", lbr.dn);
    let mut dn = Dn::from_dn_str(&lbr.dn)?;

    let Some(requested_domain) = dn.get_hostname() else {
        debug!("No domain name CN found in DN: {}", lbr.dn);
        return Err(LdapError::InvalidQuery);
    };

    // Lowercase the domain systematically to allow matches
    let requested_domain = requested_domain.to_lowercase();

    let Some(mapping) = config
        .mapping
        .iter()
        .find(|x| x.from.to_lowercase() == requested_domain)
    else {
        // TODO: we should probably return an error to the client here
        debug!("No mapping found for domain {requested_domain}");
        return Err(LdapError::InvalidQuery);
    };

    debug!(
        "Redirecting {} to {} with domain {}",
        requested_domain, mapping.backend, mapping.to
    );
    dn.set_hostname(&mapping.to, false);
    lbr.dn = dn.to_dn_string();
    let backend_dn = lbr.dn.clone();

    // We need the client to connect *and* bind to proceed here!
    let mut client = match BasicLdapClient::build(&mapping.backend).await {
        Ok(c) => c,
        Err(e) => {
            error!("A client build error has occurred: {e:?}");
            let resp_msg = bind_operror(msgid, "unable to bind");
            w.send(resp_msg).await.map_err(|err| {
                error!("Unable to send response: {err}");
                LdapError::Transport
            })?;
            // Always bail.
            return Ok(None);
        }
    };

    let valid = match client.bind(lbr, ctrl).await {
        Ok((bind_resp, ctrl)) => {
            // Almost there, lets check the bind result.
            let valid = bind_resp.res.code == LdapResultCode::Success;

            let resp_msg = LdapMsg {
                msgid,
                op: LdapOp::BindResponse(bind_resp),
                ctrl,
            };
            w.send(resp_msg).await.map_err(|err| {
                error!("Unable to send response: {err}");
                LdapError::Transport
            })?;
            valid
        }
        Err(e) => {
            error!("A client bind error has occurred: {e:?}");
            let resp_msg = bind_operror(msgid, "unable to bind");
            w.send(resp_msg).await.map_err(|err| {
                error!("Unable to send response: {err}");
                LdapError::Transport
            })?;
            // Always bail.
            return Ok(None);
        }
    };

    if valid {
        info!("Successful bind for `{request_dn}` -> `{backend_dn}`");
        Ok(Some(ClientState::Authenticated {
            request_dn,
            backend_dn,
            client,
        }))
    } else {
        Ok(None)
    }
}